Keywords: submarine pressure hulls, plastic shell instability, conical shells, ANSYS, PD5500.

This paper presents a theoretical geometrical and material non-linear analyses of fifteen un-stiffened conical shells, using the finite element computer program ANSYS, to calculate their buckling pressures. The cones buckle as a result of shell instability caused by the external hydrostatic pressure. Experimental tests were also carried to destruction of the fifteen vessels, under external hydrostatic pressure. The experimental results for the fifteen conical shells, were compared with multiple alternate theoretical methodologies, including ANSYS eigen-buckling, ANSYS nonlinear, together with other methodologies; which included PD5500 (BS5500), and the design charts produced by Ross. The ANSYS eigen-buckling results were poor; but the ANSYS nonlinear results were much more encouraging. PD5500 was too conservative, but Ross' design charts were the best and the easiest to use. Whereas most of the conical shells failed by plastic shell instability, some of the failures were initiated by axisymmetric deformation; prior to plastic shell instability taking place. The PD5500 code was hard to use and produced overly conservative results, which would lead to conservative pressure vessel designs, while the Ross design charts [1] produced good results, and were very easy to use and understand, and were not too conservative. The graphical displays from ANSYS were quite spectacular. From some of the ANSYS nonlinear analyses, it appeared that plastic axisymmetric yield initially took place at the larger ends of the cones; before triggering off plastic shell instability.

1

C.T.F. Ross, "Pressure Vessels: External Pressure Technology", 2nd Ed., Woodhead Publishers, Cambridge, UK, 2011.

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